French Onion Chicken Pasta Casserole

French onion soup may be pretty simple, but there’s something so special about that combination of flavors. The way the onions become sweet and lose all their sharpness, the contrast of the beef stock with the nutty Swiss cheese… We absolutely adore it. But since it can’t be all soup all the time, we’ve taken that fantastic flavor combo and converted it into casserole form. And, oh boy, is it a winner! All of those flavors we love with the addition of comforting pasta and hearty chicken… it’s a weeknight dinner you’ll keep coming back to.

10 oz. fettuccine noodles, broken into thirds, cooked and drained
2 cups cooked chicken, shredded
2 1/2 cups beef broth
2 large onions (5-6 cups), halved and thinly sliced
1/4 cup (1/2 stick) unsalted butter
1 tablespoon fresh thyme, minced
3 tablespoons all-purpose flour
2 cups swiss cheese, grated
1/2 tablespoon balsamic vinegar
1/2 teaspoon garlic powder
Kosher salt and freshly ground pepper, to taste
1 cup panko or seasoned breadcrumbs
2 tablespoons unsalted butter, melted

Preheat oven to 350º F and lightly grease a 9×13-inch baking dish with non-stick spray.
In a large pan or skillet over medium-high heat, melt butter and sauté onions for 6-8 minutes, or until softened. Season with thyme, garlic powder, salt and pepper.
Reduce heat to medium and cook, stirring frequently, until onions have darkened and caramelized. Add balsamic vinegar and cook for another 5 minutes.
Once caramelized, sprinkle flour over the onions and stir to incorporate. Cook for 2-3 minutes, or until flour has cooked, then stir in beef broth. Bring to a boil, then reduce heat to low and simmer for 3-5 minutes, or until thickened.
Remove from heat and stir in chicken and cooked pasta.
Transfer pasta mixture to baking dish and top with Swiss cheese. Place baking dish in oven and bake for 20 minutes.
While cooking, whisk together melted butter and seasoned breadcrumbs.
Remove baking dish from oven and top with breadcrumb topping. Return to oven and cook for another 5-8 minutes, or until golden brown.
Remove from oven and serve hot!

Adapted from Pillsbury.